In this paper,we focus all our attention on this frational space and more pricisely the fractional space,the Bessel potential space .Before we start any discussion,we give the universal definition of the Bessel potential space .
Theorem. Let which is the Bessel potential space and to some degree ,equivalent to the fractional Sobolev spaces where both of them in bounded domain, be a sequence of functions such that and weakly in . Then for any .